Patent Application
20110247333
Embodiments of the invention relate generally to steam turbines and, more particularly, to double flow low-pressure (LP) steam turbines enabling steam extraction and operation of one or both LP sections of the steam turbine.
High-temperature steam may be extracted from a steam turbine for a number of uses, such as “district heating,” wherein the high-temperature steam is utilized for residential and/or commercial heating of water and/or indoor air. The extraction of steam from known steam turbines results in a number of disadvantages, however. For example, such extraction of high-temperature steam, generally at or near an intermediate-pressure (IP) section of the steam turbine, results in a drastic decrease in IP exhaust pressure. Maintaining adequate pressure at the LP section of the steam turbine therefore requires a control valve in a crossover pipe between the IP section and the LP section. Even when using such a control valve, however, the LP section often experiences windage heating, which can decrease both the efficiency and the useful life of the LP section or the steam turbine as a whole.
In addition, as extraction of steam for many applications, such as district heating, is largely seasonal in nature, a steam turbine providing such steam must be reconfigured throughout the year, often along a continuum, to maintain adequate pressure at the LP section.
A double flow low-pressure (LP) steam turbine with an LP section that can be alternately engaged and disengaged from a drive train is provided, as are methods for its use.
In one embodiment, the invention provides a steam turbine comprising: a high pressure (HP) section; an intermediate pressure (IP) section adjacent the HP section; a first low pressure (LP) section; a second LP section; a crossover pipe connecting the IP section to the first LP section and the second LP section; a drive train extending through the HP section, the IP section, the first LP section, and the second LP section; a device for engaging and disengaging the second LP section from the drive train; a valve for alternately opening and closing a portion of the crossover pipe connecting the IP section to the second LP section; and at least one extraction port for extracting a quantity of steam from at least one of the following: the crossover pipe or an exhaust of the IP section.
In another embodiment, the invention provides a steam turbine comprising: a first low pressure (LP) section; a second LP section; a crossover pipe including a first feed connected to the first LP section and a second feed connected to the second LP section; a drive train extending through the first LP section and the second LP section; a device for engaging and disengaging the second LP section from the drive train; a valve for alternately opening and closing the second feed; and at least one extraction port for extracting a quantity of steam from the crossover pipe.
In still another embodiment, the invention provides a method of operating a double-flow low pressure (LP) steam turbine including a crossover pipe connecting an intermediate pressure (IP) section to a first low pressure (LP) section and a second LP section, the method comprising: stopping steam flow to the second LP section; disengaging the second LP section from a drive train extending through the second LP section, the first LP section, and the IP section; and extracting a first quantity of steam from at least one of the following: the crossover pipe or an exhaust of the IP section.
These and other features of embodiments of the invention will be more readily understood from the following detailed description of the various aspects of the invention, taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
It is noted that the drawings are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
Turning now to the drawings,
Steam turbine 100 of
As steam flow 170 exits IP section 120, a portion of steam flow 170 may be extracted through an extraction port 122 for other uses, such as those described herein. In known devices, such extraction is made at IP section 120 or crossover pipe 130. As noted above, however, such extraction results in a decrease in IP section steam pressure, such that the un-extracted steam, as it passes through crossover pipe 130 an on to LP sections 142, 144 has a lower pressure than if steam had not been extracted. Typically, extraction of a quantity of steam greater than a known or determinable threshold will result in a decrease in steam pressure sufficient to cause the undesirable effects noted herein, e.g., LP windage heating, even when control valves are employed in crossover pipe 130 to mitigate such pressure decreases.
A device 254 is disposed between first LP section 242 and second LP section 244, such that second LP section 244 may be alternately engaged with and disengaged from drive train 250. Mechanisms and apparatuses suitable for use as device 254 may include, for example, a clutch, a hydraulic coupling, and a gear train.
As with steam turbine 100 of
Also as with steam turbine 100 of
In
Again, steam extraction through extraction ports 222, 238 below a known or determinable threshold would have minimal effect on the operation of either LP section 242, 244. Such a threshold will vary, of course, from turbine to turbine and even within the range in which an individual turbine may be operated. In any case, such a threshold of steam extraction is equal to a quantity or rate of steam extraction at which windage heating in either or both LP sections 242, 244. Stated differently, steam extraction of a quantity or at a rate may be made, provided that the unextracted steam flow is sufficient to avoid windage heating in either or both LP sections 242, 244. While extraction port 222 is shown adjacent an exhaust of IP section 220 and extraction port 238 is shown within crossover pipe 230, such an arrangement is not essential. For example, a single extraction port (e.g., 222) may be used, additional extraction ports may be used at either location, or an extraction port may be located elsewhere adjacent IP section 220 or along crossover pipe 230. The arrangement shown in the embodiment of
As shown in
Mechanisms and apparatuses suitable for use as valve 236 may include, for example, a globe valve, a ball valve, and a butterfly valve. In addition, while valve 236 is shown within second feed 234, this is not essential. Valve 236 may be located in another portion of crossover pipe 230 that allows for selective cessation of steam flow 270 to second LP section 244 without interruption of steam flow 270 to first LP section 242.
Operation of steam turbine 200 in the state shown in
In addition, as noted above, extraction of a quantity of steam below the threshold will have minimal impact on the operation of first LP section 242 or second LP section 244. As such, extraction of a quantity of steam below the threshold may continue or be initiated during operation of steam turbine as shown in
One consequence of the ability to alternately engage and disengage second LP section 244 from drive train 250 is the movement of generator 252 from a position adjacent second LP section 244 (as in
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any related or incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
